1. Field of the Invention
Embodiments of the present invention generally relate to data storage systems, and more particularly, to write heads for thermally assisted recording.
2. Description of the Related Art
Higher storage bit densities in magnetic media used in hard disk drives have reduced the size (volume) of magnetic bits to the point where the magnetic bit dimensions are limited by the grain size of the magnetic material. Although grain size can be reduced further, the data stored within the magnetic bits may not be thermally stable. That is, random thermal fluctuations at ambient temperatures may be sufficient to erase data. This state is described as the superparamagnetic limit, which determines the maximum theoretical storage density for a given magnetic media. This limit may be raised by increasing the coercivity of the magnetic media or by lowering the temperature. Lowering the temperature may not always be practical when designing hard disk drives for commercial and consumer use. Raising the coercivity, on the other hand, requires write heads that incorporate higher magnetic moment materials, or techniques such as perpendicular recording (or both).
One additional solution has been proposed, which uses heat to lower the effective coercivity of a localized region on the magnetic media surface and writes data within this heated region. The data state becomes “fixed” once the media cools to ambient temperatures. This technique is broadly referred to as “thermally assisted (magnetic) recording” (TAR or TAMR), “energy assisted magnetic recording” (EAMR), or “heat-assisted magnetic recording” (HAMR) which are used interchangeably herein. It can be applied to longitudinal and perpendicular recording systems as well as “bit patterned media”. Heating of the media surface has been accomplished by a number of techniques such as focused laser beams or near-field optical sources. However, several issues exist when utilizing focused laser beams or near-field optical sources. One such issue is the reflection of laser light.
During recording, a wave guide of a slider is irradiated with laser light. As light is emitted from the laser, undesirable deterioration of laser light characteristics occurs due to interference with reflected laser light from a flex surface. Reflected laser light (for example, light reflected from a slider) interferes with the laser light coming from the light source, thus deteriorating or changing characteristics of the light emitted from the source, such as light wavelength. Previous solutions have proposed using an isolator, e.g., an optical element having a size of several centimeters, in order to reduce the amount of light returned to the light source. However, due to the size of the isolator, it is difficult to include an isolator within a write head, which includes components on a scale of microns.
In order to overcome deterioration of laser light characteristics, JP 2011-187111 proposes using a bent or slanted waveguide having a large diameter. However, integration of such a waveguide into a slider complicates the structure of the waveguide, and can lead to yield degradation and increased costs of production.